Titanium tetrachloride is produced by a chlorinating reaction of raw material containing titanium. The titanium-containing raw material contains a few percent of impurities such as iron or silicon in the form of oxides. Under the present circumstances, impure metal chlorides that are byproduced by chlorinating these impure oxides are treated as waste products.
These waste products are rendered harmless by washing with water, and they are separated into solid components and aqueous component. The solid component may be used as landfill material, and the aqueous component is treated as wastewater.
However, not only do the above treatments incur costs, but also titanium-rich raw material and carbon raw material, which are valuable as raw material for producing titanium tetrachloride and which are carried over while being unreacted, are contained in the solid component of the byproduct. Furthermore, chlorine, which is used in the chlorinating reaction of the titanium-containing raw material, is also contained in the form of chlorides. These valuable materials, such as unreacted raw material and chlorine components, are also wasted, and there is room for improvement from the viewpoints of cost reduction and environmental protection.
Regarding these viewpoints, Japanese Unexamined Patent Application Publication No. 2005-015250 discloses a technique in which chlorides of metals other than titanium byproduced in the production process of titanium tetrachloride and titanium metal are reacted at a high temperature so that the metal is recovered as a valuable material, and that chlorine in the metal chlorides is recovered as titanium chlorides.
However, in the above method, titanium chlorides, in which chlorine in the metal chlorides is fixed, require further treatment, and there is room for improving the cost and the process.
Furthermore, Japanese Unexamined Patent Application Publication Nos. 2011-241339 and Hei10 (1998)-314697 disclose a technique in which chlorine-containing waste product is heated so as to separate and remove chlorine gas and detoxify it, and then the product is burned and gasified.
However, these methods depend on the concept of combusting waste products, and it is necessary to treat chlorine gas generated during the process, and it is also necessary to treat other gas components during combustion. From the viewpoint of environmental protection of the Earth, there is room for improvement.
As is explained, a technique is required in which not only can recovered product byproduced in a production process for titanium tetrachloride be treated with an appropriate method so as to recover valuable material, but also, the valuable material, which can be recycled, can be recovered efficiently.
Furthermore, the price of high grade titanium raw material having a large content amount of titanium has been increasing, and as a countermeasure, a method is known in which a low grade titanium raw material having a small content amount of titanium is improved in quality to an appropriate grade (improving titanium concentration) so as to obtain high titanium-containing raw material, and thereby producing titanium tetrachloride by using this. However, also in this case, impure chlorides which are derived from the low grade titanium raw material are byproduced during a cooling process for exhaust gas, and these chlorides are also processed as a waste product, the amount of the waste product has tended to increase with increasing amounts of the low grade titanium raw material used. Thus, improvements for these problems are necessary.